The present invention relates to an air conditioner system of the type including air cooling means and air heating means and capable of maintaining any given temperature within a given space and more particularly to an air conditioner system well suited for installation on automotive vehicles.
The automobile air conditioner systems used in the early days employed a cooler and a heater separately. Later, air conditioner systems of the type in which the cooler and heater were controlled as a unit to satisfactorily control the temperature within the vehicle compartment at a constant value against a wide range of outside air temperatures, that is, the so-called reheat air mixing type came into use. Since the reheat air mixing type, is advantageous in that it is excellent in the continuity of temperature control and it also serves a dehumidifying function, air conditioner systems of this type have come into wide use.
One such automobile air conditioner system of the reheat air mixing type is disclosed for example in Japanese Unexamined Publication No. 55-36166. In this prior art system, the operating range of a refrigerant compressor is so wide that as for example, the compressor or cooling means is operated even until the outside air in temperature is so low the vehicle compartment would not be uncomfortable without any cooling and dehumidification.
In this connection, 80% of the power required for the operation of this type of air conditioner system is consumed in driving the cooling means or the refrigerant compressor.
Thus, this type of conventional air conditioner system is disadvantageous from the energy saving point of view in that an unnecessarily large amount of engine power is consumed when considered in terms of the whole year.
On the other hand, another type of automobile air conditioner system is disclosed in Japanese Unexamined Publication No. 58-156410, for example. With the automobile air conditioner system disclosed in this publication, however, as will be described later in detail, no consideration is given to the temperature of the intake air before the heat exchanging stage and therefore there is a disadvantage that the heat exchanging characteristic fails to become monotonic at the boundary between cooling and heating of the air so that the automatic control of the vehicle compartment temperature to the desired temperature is deteriorated in convergence and a considerable time is required prior to reaching a steady-state condition.
Another example of the prior art is disclosed in U.S. Pat. No. 4,416,324. However, this air conditioner system still leaves room for improvement in energy saving in that even though the desired discharged air temperature of the cooling means is shifted to an upper level when the heating means comes into operation, the cooling means is also in operation.
Other prior art literatures include U.S. Pat. Nos. 4,337,818; 4,311,188; 4,408,713; 4,460,035; 4,416,324; 4,466,480; 4,417,618; 4,375,754; 4,407,446; 4,354,547; 4,323,111; and 4,498,309; and Japanese Patent Nos. 34371 and 71618.